Field of the Invention
The present invention relates to a coplanar type oxide thin film transistor (TFT), a method of manufacturing the same, and a display panel and a display device using the same.
Discussion of the Related Art
A flat panel display (FPD) device is applied to various electronic devices such as portable phones, tablet personal computers (PCs), notebook computers, monitors, etc. Examples of FPD apparatuses include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting display devices, etc. Recently, electrophoretic display (EPD) devices are being widely used as one type of the FPD device.
In FPD devices, LCD devices display an image by using liquid crystal, and organic light emitting display devices use a self-emitting device that self-emits light.
A display panel configuring a display device includes a plurality of switching elements, for displaying an image. The switching elements may be configured with thin film transistors (TFTs). Each of the TFTs may be formed of amorphous silicon (a-Si), poly silicon, or oxide. A TFT formed of oxide is referred to as an oxide TFT.
FIG. 1 is an exemplary diagram illustrating a process of manufacturing a related art coplanar type oxide TFT.
First, as illustrated in FIG. 1 (a), a buffer 12 is coated on a substrate 11, an oxide semiconductor 13 is coated on an upper side of the buffer 12, a gate insulation layer 14 is coated on the oxide semiconductor 13, and a patterned gate 15 is stacked on an upper side of the gate insulation layer 14. When the gate insulation layer 14 is etched by using the gate 15 as a mask, as illustrated in FIG. 1 (b), a portion of the oxide semiconductor 13 is exposed.
In this case, as illustrated in FIG. 1 (b), when plasma is irradiated onto the exposed portion of the oxide semiconductor 13, the exposed area becomes conductive, and thus, a first electrode 16 and a second electrode 17 of the oxide TFT are formed. One of the first electrode 16 and the second electrode 17 is a source of the oxide TFT, and the other electrode is a drain of the oxide TFT.
As described above, the gate insulation layer 14 is etched through a dry etching process, and then, the exposed portion of the oxide semiconductor 13 becomes conductive by plasma treatment, thereby manufacturing the first electrode 16 and the second electrode 17 of the related art coplanar type oxide TFT.
However, since the gate insulation layer 14 is etched through a dry etching process for forming the first electrode 16 and the second electrode 17, the buffer 12 is etched in the dry etching process, and for this reason, a step height K can occur between the oxide semiconductor 13a and the buffer 12. Due to the step height K, a short circuit defect can occur in lines connected between the first electrode 17 and the second electrode 16.
Moreover, in depositing an insulation layer in a subsequent process, due to the step height K, step coverage problems can occur, and the gate 15 and the drain may be short-circuited with each other, causing a short circuit defect. For this reason, the reliability of a TFT is degraded.
Moreover, when the gate insulation layer 14 is over-etched, a portion of the buffer 12 may be damaged or removed.
In addition, if a light shielding layer for blocking light is provided between the substrate 11 and the buffer 12, and the gate insulation layer 14 and the buffer 12 are over-etched, the light shielding layer can be exposed or the thickness of the buffer 12 may be reduced, causing a short circuit between the light shielding layer and the gate 15.
Thus, in order to manufacture the related art coplanar type oxide TFT, the gate insulation layer 14 should be etched through the dry etching process, and due to the dry etching process, various kinds of defects can occur.